The inventive concept relates to a nitride semiconductor, and more particularly, to a semipolar nitride semiconductor structure having a semipolar characteristic, and a method of manufacturing the semipolar nitride semiconductor structure.
It is absolutely necessary to lower a price of a light emitting diode (LED) for market entry of solid state lighting. For this, it is necessary to increase productivity by increasing the size of a substrate and to reduce cost by increasing chip efficiency.
Methods to reduce costs include reducing the price of a luminaire by suppressing efficiency droop to reduce the number of chips used for a bulb, and replacing a present phosphor conversion LED with color mixing to increase efficiency. As a method of replacing a present fluorescent light by reducing the price of solid state lighting, an LED is used that increases productivity and has high efficiency and low efficiency droop, having a large substrate of 8 inches or more.
There have been many arguments on reasons for efficiency droop. Known reasons are light leakage due to many dislocations within a quantum well and an overflow of electrons due to energy band bending through a piezoelectric field. As a method of suppressing efficiency droop caused by the above-described reasons, there a nonpolar GaN substrate has been implemented. When a nonpolar substrate is used, no polarization field is generated, and thus energy band bending is prevented. Thus, overflow may be reduced, and defects occurring due to the use of a GaN bulk substrate may be reduced by more than 100 times as compared with a hetero-epitaxy method of the related art.
However, a GaN bulk substrate has a diameter of 4 to 6 inches, and the price thereof is several thousands of dollars, and thus it is difficult to apply the GaN bulk substrate for commercial purposes. Furthermore, in practice, the price of a non-polar or semipolar GaN substrate is high.